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Balancing 2 Router with ACE

Hi everybody...

A customer wants to loadbalance two router with an ACE 4710 !!

So basically ( i told him that he can do it in other way..) but ..nothing !!!

He wants to use a Loadbalancer !!!

I tested in my lab creating a similar network topology...( similar to Balance two firewalls).

But it's not necessary to have any mac-sticky enable and it doesn't matter about asimmetric routing !!

Which Predictor can let me loadbalance "per packet"  ?

In the bottom example

                   ROUTER-1 int gi 0/1 (

    WAN <------                                           <------- ACE 4710 --- Clients

                  ROUTER-2  int gi 0/1 ( 

customer want ACE4710 to send a packet to ROUTER-1 and a packet to ROUTER-2 as routers were Rservers!!

The predictor should choose the best Router ( the one that has the less number of packets in on int gi 0/1)

I tried predictor least-loaded with an snmp probe on oid ifOctentin of the interface gi 0/1..

But it works in a strange way ( rservers became MAX-LOAD and the Serverfarm stop working) !!

Any ideas ?

Thanks to all will give me some help,advise,info !!


Can you share the config of your probe and your serverfarm.

And also inyour case , i would suggest you to go with Predictor leastbandwidth.



As soon as possible i'll send you the config !!

But any advise using least-bandwith ?

Let me explain...

I know that least-bandwith is ok for Long-time-connection ( as..downloading a video clip ).

But i think customer will check using this type of test (so i'm using pretty the same in my Lab) :

One Client ( six  same processes :  ping -t -l 1500)  for an hour !!

                                               ROUTER-1 int gi 0/1 (

SERVER ( )   <--- WAN                                              <------- ACE 4710 --- Client

                                               ROUTER-2  int gi 0/1 ( 

So again ... Any good advise using predictor least-bandwith in this situation ?

Just curious, Is there any product DOES support load-balancing per packet?


Hi Alex,

Load-balancing per packet is undesireable for most kinds of traffic, so, no, there are no products doing it.


Daniel Arrondo Ostiz
Cisco Employee


The ACE doesn't support load-balancing per packet, only per connection.

For this kind of setup, you will probably achieve the best results using the simple round-robin predictor, but you can also try "leastconn". The best approach would be configuring one of the predictors, and keep it running for a few days to see the load-balancing results it gives before making the decision whether to try a different one or not



I'm trying now roundrobin !!!

But the result are not so good ..

Let me explain  :

1) One Client ( six  same processes :  ping -t -l 1500)  for an hour !!

                                               ROUTER-1 int gi 0/1 (

SERVER ( )   <--- WAN                                              <------- ACE 4710 --- Clients

                                               ROUTER-2  int gi 0/1 ( 

2) Statistic after half an hour :

    ROUTER-1 int gi 0/1 pkt in   1600

    ROUTER-2 int gi 0/1 pkt in   17800

I know that each np works indipendentely..but..why so big differences ?

Good afternoon,

This kind of test is not a good approach. As with any other kinds of traffic, the ACE will establish a connection for the ICMP traffic and keep it open for some time, so, all the traffic will basically go through one of the routers.

If you want to do a better testing, I would recommend doing a lot of HTTP requests against a web server. You should see better load-balancing in that way.


Ok Daniel...

Just to make the customer see the solution working in the Lab i'll use the scenario you tell me ( a lot of HTTP requests..).

Anyway can be better/useful to use parameter "use-same-np" ( serverfarm parameter) just during the demo to the customer ,without using "hw-module cde-same-port-hash (global conf parameter)" as it is advise in some release notes of ACE software ...

In other words can be useful this parameter ( using roundrobin predictor ) to have a better balance between the two router ?


Thanks and best regards

No, I would not touch any of these two parameters. The normal load-balancing should already be good enough to prove that the system is working as expected


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